Batteries in seasonal vehicles such as boats, farm equipment, RVs, in some military equipment, antique cars, and other vehicles used infrequently or only seasonally tend to lose their charge, requiring recharging at various use intervals. Conventional fast battery chargers are large and cumbersome, use a substantial amount of electricity, and charge at a faster rate than the battery can accept. When being charged with a conventional fast charger, the voltage and amperage of the battery will typically rise at a faster rate than the battery potential. Thus, when the voltage and amperage reach a level indicating that the battery is fully charged, the battery charger will be disconnected or turned off. The battery will then begin to equalize the voltage, amperage and potential, with the voltage and amperage levels dropping and the potential increasing until equalization is reached. Because of the variation in the voltage, amperage, and potential levels at the time full charge is indicated, the battery will actually be charged to only about 80% of its capacity following equalization. Thus, the prior art fast chargers cannot charge a battery to 100% of its capacity.
Batteries repeatedly charged in this fashion reduces the capacity of the battery such that the battery will begin to lose the ability to accept a full 100% charge of the original capacity. Additionally, the use of a fast battery charger often causes rapid expansion of the battery fluid and the generation of gases, thus requiring the removal of the battery caps while charging the battery. Failure to remove the caps may result in explosion of the caps causing damage or total destruction of the battery. Thus, marine, recreational vehicle, and other infrequently used batteries are protected under substantially shorter warranty periods, often less than one-half the length of the warranty periods for regularly used batteries, such as car batteries.
Trickle chargers, another conventional type battery charger, are slow battery chargers, charging the battery with only one-to-three amps of charge at a time. A slow charge will bring the battery to full charge and alleviates having to remove the battery caps while charging. However, if left on the battery for an extended length of time after the battery has obtained full charge, the trickle charger will damage the battery and may destroy it completely.
Due to the slow rate at which the trickle charger charges the battery, the charger must be connected to the battery a substantial period of time prior to the use of the boat or vehicle, prohibiting spontaneous use thereof.
In one attempt to overcome the foregoing problems, fast and slow battery chargers were designed to include built in features for automatic turn off of the charger once the voltage of the battery indicated a full charge. In such chargers, once the voltage drops to a predetermined level, the charger is automatically turned back on to again recharge the battery until the voltage reaches the full charge level. Although the battery is automatically recharged, this cycling process reduces the life of the battery. Depending upon the cycling range of the particular charger, the user may decide to use the vehicle at a point where the voltage of the battery has dropped to a level where the charger is about to begin recharging the battery.
Many fishing boats have a driving battery and two 12-volt batteries connected as a 24-volt power source for operation of a trolling motor. Thus, three chargers were required for charging each of the three batteries simultaneously.